Ventricular assist devices, known as VADs, often include an implantable blood pump and are used for both short-term (i.e., days, months) and long-term applications (i.e., years or a lifetime) where a patient's heart is incapable of providing adequate circulation, commonly referred to as heart failure or congestive heart failure. According to the American Heart Association, more than five million Americans are living with heart failure, with about 670,000 new cases diagnosed every year. People with heart failure often have shortness of breath and fatigue. Years of living with blocked arteries and/or high blood pressure can leave a heart too weak to pump enough blood to the body. As symptoms worsen, advanced heart failure develops.
A patient suffering from heart failure may use a VAD while awaiting a heart transplant or as a long term destination therapy. A patient may also use a VAD while recovering from heart surgery. Thus, a VAD can supplement a weak heart (i.e., partial support) or can effectively replace the natural heart's function.
The flow rate of blood pumped by a VAD is an important parameter for both control of the blood pump and for informing a health care professional regarding the level of circulatory support provided to the patient by the VAD. Direct measurement of blood flow rate has several drawbacks with existing technology. For example, the addition of components (e.g., a flow sensor) may increase complexity and reduce reliability. It is also generally undesirable to place structures in the flowpath because they can lead to thrombosis. Moreover, existing flow sensors suffer from drift and other factors which contribute to imprecise measurements over time.
Accordingly, existing VADs generally rely on an estimation of flow rate through the pump by indirect measurements. For example, the blood flow rate in a VAD can be estimated based on the amount of electrical power consumed by the VAD.
There is a need for improved devices and methods for measuring or estimating flow rate in a pump.
Additionally, there is the need for devices and methods for measuring clinical and/or pump parameters.